The present invention relates generally to apparatus and systems for supporting surgical and other instruments. Some surgical procedures include use of a variety of instruments. In some of these procedures, it is required that instruments, such as a retractor, be maintained in a single position for an extended period of time, such as an hour or more. During this time, other instruments can be used to perform other aspects of the surgery. Because it may be difficult or undesirable to manually hold a position of an instrument for such lengths of time, mechanical and/or electromechanical arms can be used to hold the position of the instrument while other aspects of the procedure are performed. Some arms can be adjustable such that a position of the arm can be adjusted before or during the procedure.